A Tale of Two Tubers

November 16, 2019

Few topics have sparked more discussion among my old garden club buddies than the age-old conundrum: What is the difference between sweet potatoes and yams?


Grocers use both terms when labeling bins of fresh tubers, but I doubt many of us have eaten real yams. Yams, Dioscorea, are a food staple throughout the islands of the South Pacific, Southeast Asia and tropical Africa. There are 600 species of yams. Many of the tubers are similar in size to potatoes; however, some require teams of able-bodied men to harvest each one! The huge ones are generally roasted over an open fire for community feasts.


Yams (right) are quite bland and loaded with carbohydrates. Usually they are served with spicy sauce.


The sweet potato, Ipomoea batatas, is a New World member of the morning glory family. Sweet potatoes were such a hit in Spain that the Spanish introduced this new crop into their colony the Philippines. From there it spread to China and Southeast Asia. Its cultivation is limited to warmer climates because it requires a sustained period of temperatures above 70 degrees to mature.


Next spring try growing this beautiful crop. Divide a tuber from the grocery store into “eyes” and place them in a warm, sandy starter mix. When shoots--these are called "slips" in gardening for some reason--are eight to 12 inches long, pull them from the seed roots and plant them in a sunny area. Keep them watered and hope for hot weather. Under these conditions, they quickly root and grow. Harvest before frost because decay in the vine passes down to the roots.


(Photos: Above, raw sweet potatoes. Below, cooked sweet potatoes in cans, labeled "Yams." Thanks a lot, Bruce--this doesn't help!)


 In our region, sweet potatoes are generally not planted until late in the spring, the latter part of May, say, when the ground is quite warm, as opposed to Irish potatoes which are planted in February or March. Then sweet potatoes are harvested mostly in October.


An interesting "side-crop" for sweet potato growers is their foliage, which looks like morning glory leaves, only larger, and like morning glories will spread over your garden like a sea at high tide. You can keep these in check by picking bagfuls of the leaves and cooking them like turnip greens.


But back to our yam-sweet potato motif: Sweet potatoes with darker flesh contain higher concentrations of beta carotene and are moister as well as sweeter than lighter-colored varieties. These command a higher price in the market and are often labeled “yams.” 


Check your yam can. The main ingredients are water and sweet potatoes.


Master gardener Ann Bartlett spends the warmer months happily tending the ornamental beds that surround her home but as the winter approaches sometimes finds herself in the supermarket reading the cans suspiciously. Email her at arose56@hamilton.net.

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